Print head for additive manufacturing

ABSTRACT

An additive manufacturing system may include a carrier, a set of rails coupled to the carrier, and a transition housing movably attached to the set of rails. The additive manufacturing system may include an extruder having an extruder barrel coupled to the transition housing, and a melt pump fixedly attached to the carrier. The melt pump may be in fluid communication with the extruder barrel. Additionally, the additive manufacturing system may include a nozzle in fluid communication with the melt pump, and a roller rotatable about the nozzle.

TECHNICAL FIELD

Aspects of the present disclosure relate to apparatus and methods forfabricating components. In some instances, aspects of the presentdisclosure relate to apparatus and methods for fabricating components(such as, e.g., automobile parts, medical devices, machine components,consumer products, etc.) via additive manufacturing techniques orprocesses, such as, e.g., three-dimensional (3D) printing.

BACKGROUND

Additive manufacturing techniques and processes generally involve thebuildup of one or more materials, e.g., layering, to make a net or nearnet shape (NNS) object, in contrast to subtractive manufacturingmethods. Though “additive manufacturing” is an industry standard term(ASTM F2792), additive manufacturing encompasses various manufacturingand prototyping techniques known under a variety of names, including,e.g., freeform fabrication, 3D printing, rapid prototyping/tooling, etc.Additive manufacturing techniques may be used to fabricate simple orcomplex components from a wide variety of materials. For example, afreestanding object may be fabricated from a computer-aided design (CAD)model.

A particular type of additive manufacturing is commonly known as 3Dprinting. One such process commonly referred to as Fused DepositionModeling (FDM) or Fused Layer Modeling (FLM) comprises melting a thinlayer of thermoplastic material, and applying this material in layers toproduce a final part. This is commonly accomplished by passing acontinuous thin filament of thermoplastic material through a heatednozzle, or by passing thermoplastic material into an extruder, with anattached nozzle, which melts it and applies the thermoplastic materialand applies the melted thermoplastic material to the structure beingprinted, building up the structure. The heated material may be appliedto the existing structure in layers, melting and fusing with theexisting material to produce a solid finished part.

The filament used in the aforementioned process may be produced by, forexample, using an extruder, which may include a steel extruder screwconfigured to rotate inside of a heated steel barrel. Thermoplasticmaterial in the form of small pellets may be introduced into one end ofthe rotating screw. Friction from the rotating screw, combined with heatfrom the barrel may soften the plastic, which may then be forced underpressure through a small round opening in a die that is attached to thefront of the extruder barrel. In doing so, a “string” of material may beextruded, after which the extruded string of material may be cooled andcoiled up for use in a 3D printer or other additive manufacturingsystem.

Melting a thin filament of material in order to 3D print an item may bea slow process, which may be suitable for producing relatively smallitems or a limited number of items. The melted filament approach to 3Dprinting may be too slow to manufacture large items. However, thefundamental process of 3D printing using molten thermoplastic materialsmay offer advantages for the manufacture of larger parts or a largernumber of items.

In some instances, the process of 3D printing a part may involve atwo-step process. For example, the process may utilize a large printbead to achieve an accurate final size and shape. This two-step process,commonly referred to as near-net-shape, may begin by printing a part toa size slightly larger than needed, then machining, milling or routingthe part to the final size and shape. The additional time required totrim the part to a final size may be compensated for by the fasterprinting process.

Print heads of additive manufacturing machines used to printthermoplastic material in relatively large beads have generally includeda vertically mounted extruder flowably connected to a nozzle to depositthe bead of material through the nozzle onto a surface and/or a partbeing printed. These traditional print heads may include an oscillatingplate surrounding the nozzle, the plate being configured to oscillatevertically to flatten the bead of material against the part or surfacebeing printed on. Such traditional print heads may have severaldrawbacks including a tendency to trap air between layers as the layersare tapped together, uneven flow of material being printed, difficultyin servicing the machine (e.g., replacing extruder screws), anddifficulty in scaling the machine to process material at a higher rateof throughput.

SUMMARY

Aspects of the present disclosure relate to, among other things, methodsand apparatus for fabricating components via additive manufacturing or3D printing techniques. Each of the aspects disclosed herein may includeone or more of the features described in connection with any of theother disclosed aspects.

The additive manufacturing system disclosed herein may improve theability to evenly bond adjoining layers of deposited material withouttrapping air between them, maintain even material flow at any printspeed, permit easy removal and replacement of the extruder screw, and/oreasy removal and replacement of the entire melt core (including a feedhousing, extruder, and melt pump) with a larger or smaller melt core.

The additive manufacturing machine disclosed herein may include acarrier equipped with a servomotor and gearbox assembly. The servomotorand gearbox assembly may be slidably connected to the carrier, e.g., viaone or more tracks. Additionally, or alternatively, the servomotor andgearbox assembly may be hingedly connected to the carrier so that theservomotor and gearbox assembly may swing clear of (e.g., so as not tocross) a longitudinal axis of the carrier. This servomotor and gearboxassembly may be coupled via a transition housing to a feed housing. Thefeed housing may be attached to the extruder barrel such that anextruder screw disposed inside the extruder barrel extends through thefeed housing and attaches to the output shaft of the gearbox through acoupling.

The extruder barrel may be equipped with multiple heating elements. Theheating elements may circumferentially surround at least a portion ofthe extruder barrel. Also, the extruder barrel may include or receive aplurality of thermocouples operably connected to a controller, e.g., viaa transition box, to monitor and/or control the temperature of theextruder barrel at different heating zones along the extruder barrel.The output of the extruder barrel may be attached to the input of a meltpump (e.g., a polymer melt pump) so that material flowing from theextruder feeds into the melt pump. The melt pump may be operated by aservomotor, e.g., via a gearbox, thereby enabling the melt pump assemblyto precisely meter the material to the nozzle (e.g., a heated nozzle)for deposition on a surface and/or the part being printed. As the nozzlemoves, a roller may be directed by the controller to follow the nozzleso that the roller flattens and/or compresses the deposited material.

The melt pump may be attached (e.g., fixedly attached, bolted, etc.) toa bottom or underside of the carrier. Other components may be movablyattached to one or more rails affixed to the carrier. For example, theextruder, the feed housing, a transition housing, a gearbox, and aservomotor driving the extruder, may be movably connected to the one ormore rails. The components may be connected to the rails directly and/orvia a support assembly. The applicator head, including the nozzle, maybe coupled to the melt pump. Accordingly, the applicator head, alongwith the melt pump, may move with the carrier while other components ofthe print head (e.g., the extruder) may be displaced along the rails ofthe carrier. With the components configured in this manner, the movementof the applicator head, and thus the nozzle remains constant even ifother components of the print head (e.g., the extruder) are displacedand/or replaced with a component of a different size.

Several components of the assembly, such as, e.g., the extruderservomotor, feed housing, melt pump gearbox mounting plate, and theroller in the applicator head assembly, may be cooled via a coolingsystem. The cooling system may include liquid cooling components and/orair cooling components. The cooling system may allow the print head toprocess materials at relatively high temperatures which might otherwisedamage components. For example, the applicator head assembly may includea cooling system, or part thereof, to cool the roller. In such a coolingsystem, liquid may be passed into the applicator head through one ormore passageways to an axle of the roller before returning to a chilleror other heat exchanger. By cooling the roller, materials commonlyprocessed at higher temperatures, such as, e.g., polyphenylene sulfide(PPS), may adhere less to the roller during operation.

The cooling system may enable the roller to evenly bond adjoining layersand limit or eliminate air trapped between adjoining layers.Additionally, a duct system may cool a portion of the extruder barrel,e.g., via a blower surrounding a portion of the extruder barrel, toimprove control over the temperature of molten material at the outlet ofthe extruder barrel.

The combination of the extruder and the melt pump, as opposed to only anextruder having no associated melt pump, may enable the additivemanufacturing machine to utilize different extruder screw designs havingdifferent desirable characteristics, while maintaining even flow ofmaterial during operation. The melt pump may adjust the flow of materialreceived from the extruder thereby compensating for changes in flowcaused by replacing the extruder screw with a different design (e.g., ascrew having a different pitch, length, or thread).

The configuration of the additive manufacturing machine may allowrelatively easy removal and replacement of the extruder screw. Forexample, replacement of the extruder screw may begin by decoupling theextruder screw from the servomotor and gearbox assembly and decouplingthe feed housing from the transition housing. The servomotor, gearboxand transition housing may be slid upward, e.g., along rails attached tothe carrier, until the parts sufficiently clear the extruder screw. Thenthe entire mechanism may be rotated sufficiently to permit removal ofthe extruder screw.

This same configuration may allow relatively easy removal andreplacement of the melt core (e.g., the feed housing, extruder, and meltpump assembly) of the additive manufacturing machine. Changing the meltcore may alter the throughput of the print head. Removal of the meltcore may begin with disconnecting the servomotor, the gearbox, and thetransition housing assembly from the feed housing and the extruderscrew. Then, the barrel heaters and thermocouples may be unplugged fromthe controller. Next, the servomotor, gearbox, and transition housingassembly may then slid upward along the rails of the carrier andsecured. The melt pump may then be disconnected from the carrier so thatthe entire melt core may be removed. A different melt core (e.g., adifferent sized melt core) may be attached to the carrier in place ofthe previous melt core. Next, the barrel heaters and thermocouples maybe replaced and plugged in to the controller. Then, the servomotor,gearbox, and transition housing assembly may be lowered and attached tothe feed housing and extruder screw, respectively, to complete thereplacement of the melt core.

In one embodiment of the present disclosure, an additive manufacturingsystem may include a carrier, a set of rails coupled to the carrier, anda transition housing movably attached to the set of rails. The additivemanufacturing system may include an extruder having an extruder barrelcoupled to the transition housing, and a melt pump fixedly attached tothe carrier, the melt pump in fluid communication with the extruderbarrel. Additionally, the additive manufacturing system may include anozzle in fluid communication with the melt pump, and a roller rotatableabout the nozzle.

In an additional or alternate embodiment of the present disclosure, anadditive manufacturing system may include a CNC machine, a carriersupported by the CNC machine. The carrier may be movable along aplurality of axes. The additive manufacturing machine may include a setof rails mounted on the carrier, and an extruder drive assembly slidablyattached to the set of rails. The extruder drive assembly may beoperably coupled to an extruder. Also, the additive manufacturingmachine may include a melt pump fixedly attached to the carrier, and anozzle in fluid communication with the melt pump. The nozzle may beconfigured to receive a flowable material from the melt pump.Additionally, the additive manufacturing machine may include a roller.

In an additional or alternate embodiment of the present disclosure, amethod of servicing an additive manufacturing system may includedetaching an extruder drive assembly from an extruder, and moving theextruder drive assembly relative to the extruder along a set of railsmounted to a carrier. The method may further include replacing at leasta part of the extruder and reattaching the extruder drive assembly tothe extruder.

As used herein, the terms “comprises,” “comprising,” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchas a process, method, article, or apparatus. The term “exemplary” isused in the sense of “example,” rather than “ideal.” As used herein, theterms “about,” “generally,” “substantially,” and “approximately,”indicate a range of values within +/−5% of the stated value unlessotherwise stated.

It may be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the disclosure, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary aspects of the presentdisclosure and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 is a perspective view of an exemplary CNC machine operablepursuant to an additive manufacturing process to form articles or parts,according to an aspect of the present disclosure;

FIG. 2 is an enlarged perspective view of an exemplary carrier andextruder of the exemplary CNC machine shown in FIG. 1;

FIG. 3 is an enlarged perspective view of an exemplary carrier andapplicator head assembly of the exemplary CNC machine shown in FIG. 1;

FIG. 4 is an enlarged cutaway view of the exemplary applicator headassembly shown in FIG. 3;

FIG. 5 is a perspective view of the exemplary carrier and extruder shownin FIG. 2;

FIG. 6A is a side view of the exemplary carrier and extruder shown inFIG. 2; and

FIG. 6B is a rear view of the exemplary carrier and extruder shown inFIG. 2.

DETAILED DESCRIPTION

The present disclosure is drawn to, among other things, methods andapparatus for fabricating components, parts, or articles via additivemanufacturing such as, e.g., 3D printing. Specifically, the methods andapparatus described herein comprise a print head configured to depositmaterial at a relatively constant flow rate under a variety ofconfigurations, bond layers of deposited material together with minimalor no air trapped between layers, and permit ease of maintenance andreplacement of parts.

For purposes of brevity, the methods and apparatus described herein willbe discussed in connection with the fabrication of parts fromthermoplastic materials. However, those of ordinary skill in the artwill readily recognize that the disclosed apparatus and methods may beused with any flowable material suitable for additive manufacturing.

Referring to FIG. 1, there is illustrated a CNC machine 1 embodyingaspects of the present disclosure. CNC machine 1 may include acontroller operatively connected to CNC machine 1 for displacing anapplicator head 43 and a print head 99 (FIG. 2) along a longitudinalline of travel, or x-axis, a transverse line of travel, or a y-axis, anda vertical line of travel, or z-axis, in accordance with a program,(e.g., a CNC program) inputted or loaded into the controller forperforming an additive manufacturing process to form a desiredcomponent, as will be described in further detail below. CNC machine 1may be configured to print or otherwise build 3D parts from digitalrepresentations of the 3D parts (e.g., AMF and STL format files).

For example, in an extrusion-based additive manufacturing system (e.g.,a 3D printing machine), a 3D part may be printed from a digitalrepresentation of the 3D part in a layer-by-layer manner by extruding aflowable material (e.g., thermoplastic material with or withoutreinforcements). The flowable material may be extruded through anextrusion tip or nozzle 51 (FIGS. 3 and 4) carried by applicator head 43of the machine 1, and the flowable material may be deposited as asequence of beads or layers on a substrate in an x-y plane. Theextruded, flowable material may fuse to a previously deposited layer ofmaterial and may solidify upon a drop in temperature. The position ofapplicator head 43 relative to the substrate may then be incrementallyadvanced along a z-axis (perpendicular to the x-y plane), and theprocess may then be repeated to form a 3D part resembling the digitalrepresentation.

CNC machine 1, as shown in FIG. 1, includes a bed 20 provided with apair of transversely spaced side walls 21 and 22, a printing gantry 23and a trimming gantry 36 supported on opposing side walls 21 and 22, acarriage 24 mounted on printing gantry 23, a carrier 25 mounted oncarriage 24, an extruder 61, and applicator head 43 mounted on carrier25. Located on bed 20 between side walls 21 and 22 is a worktable 27provided with a support surface. The support surface may be disposed inan x-y plane and may be fixed, or displaceable, along an x-axis and/or ay-axis. For example, in a displaceable version, worktable 27 may bedisplaceable along a set of rails mounted to bed 20. Displacement ofworktable 27 may be achieved using one or more servomotors and one ormore of guide rails 28 and 29 mounted on bed 20 and operativelyconnected to worktable 27. Printing gantry 23 is disposed along they-axis, supported on side walls 21 and 22. In FIG. 1, printing gantry 23is mounted on the set of guide rails 28 and 29, which are located alonga top surface of side walls 21 and 22. In some examples, the CNC machine1 may include a vertical worktable (not shown). The vertical worktablemay be attached to the worktable 27, bed 20, or the support surfaceand/or rails of worktable 27, as described above.

Printing gantry 23 may either be fixedly or displaceably mounted, and insome aspects, printing gantry 23 may be disposed along the x-axis. In anexemplary displaceable version, one or more servomotors may controlmovement of printing gantry 23. For example, one or more servomotors maybe mounted on printing gantry 23 and operatively connected to tracks,e.g., guide rails 28, 29, provided on the side walls 21 and 22 of bed20.

Carriage 24 may supported on printing gantry 23 and may be provided witha support member 30 mounted on and displaceable along one or more guiderails 31, 32 and 33 provided on printing gantry 23. Carriage 24 may bedisplaceable along the y-axis on one or more guide rails 31, 32 and 33by a servomotor mounted on the printing gantry 23 and operativelyconnected to support member 30. Carrier 25 may be mounted on one or morevertically disposed guide rails 34 and 35 supported on carriage 24 fordisplacement of carrier 25 relative to carriage 24 along the z-axis.Carrier 25 may be displaceable along the z-axis by a servomotor mountedon carriage 24 and operatively connected to carrier 25.

As shown in FIG. 2, a print head assembly 99 may include carrier 25 andone or more components attached to carrier 25 including, but not limitedto, one or more rails (e.g., rails 44 and 45), extruder 61, a gearbox39, a servomotor 38, and a transition housing 37. Print head assembly 99may include additional components as described below. Extruder 61 mayinclude a feed housing 40 and an extruder barrel 42. Extruder 61 may bedriven, by servomotor 38, which may be operatively connected to extruderscrew 80 (FIG. 5) via gearbox 39. Gearbox 39 may be physically and/oroperably attached to extruder 61 by a transition housing 37. Transitionhousing 37 may be detachably connected to extruder 61, e.g., viaextruder barrel 42. As discussed further below, transition housing 37,gearbox 39, and servomotor 38 may be collectively referred to as the“extruder drive assembly.” The extruder drive assembly may be movably,e.g., slidably, attached to rails 44 and 45 mounted on carrier 25. Insome examples, extruder 61 may be movably attached to rails 44 and 45.Optionally, one or more components of print head assembly 99 may beattached to rails 44 and 45 via a support assembly. The support assemblymay be movable along rails 44 and 45 in line with a longitudinal axis ofcarrier 25. The support assembly may include a hinge or other mechanismpermitting rotation of one or more components attached to the supportassembly. For example, the extruder drive assembly may be coupled to aportion of the support assembly (e.g., via transition housing 37) suchthat the portion of the support assembly supporting the extruder driveassembly is rotatable with respect to carrier 25 (e.g., rotatable alonga longitudinal axis offset from the longitudinal axis of carrier 25).The support assembly may be configured to move and rotate the extruderdrive assembly so that the extruder drive assembly clears space for theremoval and/or maintenance of extruder 61, as will be described infurther detail below.

With continued reference to FIG. 2, one or more heaters 41 may surroundat least a portion of extruder barrel 42, as shown. In some embodiments,heaters 41 may circumferentially surround a portion of extruder barrel42. Heaters 41 may be disposed along a portion or along the entirelength of extruder barrel 42.

A material (e.g., thermoplastic material) may be introduced into anopening of feed housing 40. Those of ordinary skill will recognize thatthe material may be of any suitable material, for example, thermoplasticmaterial, and that the material may be delivered to extruder barrel 42in any suitable size and/or configuration, e.g., as pellets. In anexemplary embodiment, the material introduced into extruder barrel 42may be heated by the friction generated from rotation of extruder screw80 (FIG. 5) and/or by one or more heaters 41 disposed along the lengthof extruder barrel 42. In an exemplary embodiment, once the material hasmelted, the molten material may be forced under pressure by extruderscrew 80 further into extruder barrel 42 and out of a terminal end orbottom opening of extruder barrel 42. Next, the flowable material may bedelivered to nozzle 51 (FIGS. 3 and 4) to be deposited, as furtherdescribed below.

As shown in FIG. 3, also mounted to carrier 25 (e.g., fixedly mounted tocarrier 25) may be a positive displacement melt pump 62 (e.g., a gearpump) which may be driven by a servomotor 63, through a gearbox (notshown). Melt pump 62 may be in fluid communication with extruder barrel42 to receive molten plastic from extruder 61, shown in FIG. 2, andmeter out precise amounts of material at a controlled flow rate tonozzle 51 so as to print the part or component. The combination ofextruder 61 and melt pump 62 may enable CNC machine 1 to utilizedifferent extruder screws 80 having different desirable characteristics.For example, CNC machine 1 may be configured to use various extruderscrews 80 having different characteristics including, but not limitedto, length, pitch, helix angle, diameter, root, channel depth, channelwidth, channel flight, pushing flight, and trailing flight. Differentextruder screws 80 may produce different material flow rates of materialbeing extruded. Melt pump 62 may enable and/or maintain a relativelyconstant flow rate of material provided to nozzle 51 regardless of theextruder screw 80 used. For example, melt pump 62 may increase and/ordecrease the flow rate of material sent to nozzle 51 in order tocompensate for the flow rate of material received from extruder 61.

With reference to FIGS. 3 and 4, applicator head 43 may include ahousing 46 having a rotary union mounted therein. Such a rotary unionmay include an inner hub 76 rotatably mounted within and relative to anouter housing 75. For example, inner hub 76 may rotate about alongitudinal axis thereof relative to outer housing 75 via one or moreroller bearings 49. A carrier bracket 47 may be mounted, e.g., fixedlymounted to inner hub 76, journaled in roller bearing 49. Roller bearing49 may allow roller 59 to rotate about nozzle 51.

Roller 59 may be oriented tangentially to nozzle 51. Roller 59 may bemounted relative to nozzle 51 so that material, e.g., one or more beadsof flowable material (such as thermoplastic), discharged from nozzle 51are smoothed, flattened, leveled, and/or compressed by roller 59, asdepicted in FIG. 4. One or more servomotors 60 (FIG. 3) may beconfigured to move, e.g., rotationally displace, carrier bracket 47 viaa pulley 56 and belt 65 arrangement. In some embodiments, carrierbracket 47 may be rotationally displaced via a sprocket and drive-chainarrangement (not shown), or by any other suitable mechanism.

In some arrangements, roller 59 may be removably mounted to CNC machine1. For example, different sized or shaped rollers 59 may beinterchangeably mounted on CNC machine 1, depending on, e.g., the typeof material 53 and/or desired characteristics of the rows (e.g., plies)of deposited flowable material formed on worktable 27.

In the course of fabricating an article or component, pursuant to themethods described herein, the controller of CNC machine 1, in executingthe inputted program, may control several servomotors described above todisplace gantry 23 along the x-axis, displace carriage 24 along they-axis, displace carrier 25 along the z-axis, and/or rotate carrierbracket 47 about the z-axis while nozzle 51 deposits material 53 androller 59 compresses the deposited material 53. In some embodiments,roller 59 may compress material 53 in uniform, smooth rows.

A circumferential outer surface of inner hub 76 may include or define apulley 56. For example, as shown in FIG. 3, pulley 56 may include aradially outward-most portion of inner hub 76. Although pulley 56 isdepicted as being integral with inner hub 76, pulley 56 may be separateand discrete from inner hub 76. Additionally, inner hub 76 may includean opening having a dimension (e.g., diameter) sufficient to allownozzle 51 to pass therethrough.

Outer housing 75 may include one or more barb fittings 67, 68. Coolantmay enter a barb fitting 67 and may be introduced inside of housing 46of applicator head 43. Each barb fitting 67 and 68 may be fluidlycoupled to one or more passages extending through applicator head 43.For example, each of barb fittings 67 and 68 may be coupled to one ormore coolant passages 70. As shown in FIG. 4, coolant passages 70 mayextend between outer housing 75 and inner hub 76. Additionally, coolantpassages 70 may couple to quick connect fitting 72. Quick connectfitting 72, in turn, may be fluidly coupled to an interior bore,passage, or lumen extending through the axle 73 to directly cool theaxle 73, and thereby, roller 59. Each coolant passage 70 may be disposedwithin applicator head 43 to direct the coolant within applicator head43 during operation of CNC machine 1, e.g., when printing a part.

Regardless of the configuration, orientation, shape, or arrangementthereof, barb fitting 67, coolant passages 70, quick connect fitting 72,axle 73, and barb fitting 68 may collectively form a cooling circuit forcycling or otherwise introducing and removing coolant from applicatorhead 43. For example, an inlet portion of barb fitting 67 may be fluidlyconnected to a source of coolant (not shown). Once within applicatorhead 43, the coolant may absorb heat and may cool outer housing 75,inner hub 76, and axle 73 as it flows therethrough. In addition, due tothe proximity of roller 59 to axle 73, passage of coolant through axle73 may result in likewise cooling of roller 59. The coolant may exitfrom one or more barb fittings 68 and may return to a chiller to becooled back down to an appropriate temperature.

The coolant may be cooled down to a temperature below that at whichdeposited material 53 may begin to adhere to roller 59. This temperaturemay vary depending on the type of material 53 used and may be below themelting point of that material 53. For example, cooling the axle 73, andthereby roller 59, to an operating temperature may reduce adhesion tothe roller 59 by certain materials processed at relatively hightemperatures, such as, e.g., polyphenylene sulfide (PPS). In someexamples, the coolant may be a liquid coolant, such as, e.g., water,antifreeze, ethylene glycol, diethylene glycol, propylene glycol,betaine, or any other suitable liquid coolants or combinations thereof.The cooling system may enable the roller 59 to compress depositedmaterial 53 so that adjoining layers are smoothly and evenly bondedtogether with little or no air trapped between layers.

Additionally, or alternatively, the cooling system may include one ormore components configured to air cool part of the additivemanufacturing machine. With reference to FIG. 5, a portion of theextruder barrel 42 and at least a portion of one or more heaters 41(e.g., two heaters 41) may be contained within a duct system 82 mountedalong the extruder barrel 42. The duct system 82 may circumferentiallysurround and/or enclose a portion of the extruder barrel 42 and/or aportion of one or more heaters 41. The duct system 82 may cool a portionof the extruder barrel using a blower 83. The blower 83 may include afan or other devices for circulating and/or cooling air. The duct system82 may be attached to the carrier 25 and/or the extruder 61 adjacent themelt pump 62. The blower 83 may be coupled to the carrier 25 oppositethe servomotor 63 that drives the melt pump 62. The duct system 82 mayimprove control of the temperature of material 53 at the distal oroutput end of the extruder 61. For example, the duct system 82 mayprevent the material within the extruder 61 from raising above aspecific temperature, including, but not limited to, an operatingtemperature or a temperature at which the flowable material 53 willburn-on the extruder 61 and/or melt pump 62.

With continued reference to FIG. 5, print head assembly 99 of CNCmachine 1 may collectively refer to carrier 25 and the components ofmachine 1 connected thereto. For example, print head assembly 99 mayinclude one or more of extruder 61, gearbox 39, servomotor 38, feedhousing 40, duct system 82, melt pump 62, applicator head 43 (FIG. 4),and/or nozzle 51 (FIG. 4). Melt pump 62 may be fixedly attached to abottom portion of the carrier 25. Other components of print head 99(e.g., extruder 61, transition housing 37, servomotor 38, and gearbox39) may be movable via a set of rails 44 and 45 mounted to carrier 25.Therefore, as components of the CNC machine 1 are replaced to operateCNC machine 1 at different output levels (which may be measured inlbs./hr., for example), the height of the nozzle 51 may be kept constantwith respect to carrier 25 even if the length(s) and/or height(s) of oneor more of extruder barrel 42, extruder screw 80, transition housing 37,servomotor 38, and gearbox 39 change. Keeping the height of the nozzle51 constant with respect to the carrier through various configurationsof the CNC machine 1 may reduce the complexity and steps involved inchanging the operating parameters of CNC machine 1, e.g., a tool pathand/or movement of nozzle 51.

As noted above, the extruder drive assembly may be attached to rails 44and 45 via a support assembly. The support assembly may include a hingeor other mechanism permitting rotation of the extruder drive assemblyoffset from a longitudinal axis of extruder 61 and/or carrier 25.Additionally, the support assembly may include one or more bearings topermit movement along rails 44 and 45.

As shown in FIG. 5, for example, the support assembly may include ahinge that is movably attached to rails 44 and 45 via a support plate85. The support plate 85 of the support assembly may be slidablyconnected to rails 44 and 45, for example by one or more slidingbearings. The hinge may include a pair of hinge leafs 86 and 87 and ahinge pin 89. Hinge leaf 86 may be fixedly coupled to support plate 85.Hinge leaf 87 may connect hinge leaf 86 to transition housing 37 via ahinge pin 89. Hinge leaf 87 may be rotatably movable between an openposition (FIG. 5) and a closed position (FIG. 2), and may rotate up to180 degrees. Thus, hinge pin 89 may provide an axis about which theextruder drive assembly may rotate that is offset from a longitudinalaxis of extruder 61 and/or carrier 25, as can be seen in FIG. 5. Aremovable stop block 90 may be employed to lock the support plate 85 ata particular vertical position on rails 44 and 45 before hinge leaf 87is rotated from the closed position to the open position.

Hinge leaf 87 may be rotated about an axis defined by hinge pin 89 toopen or close the hinge. When in a closed position, inner wall surfacesof hinge leafs 86 and 87 are brought adjacent to, and/or into contactwith, each other, and a rear surface of transition housing 37 is broughtadjacent to and/or into contact with, support plate 85. As can be seenin FIG. 5, transition housing 37, servomotor 38, and gearbox 39 may berotatable together with hinge leaf 87. A fastener such as a bolt may beused to fix transition housing 37 to support plate 85 in the closedposition.

The configuration of CNC machine 1 may facilitate servicing of CNCmachine 1 and/or replacement of one or more components of CNC machine 1.For example, extruder screw 80 may be replaced with a different extruderscrew 80 having the same or different characteristics. A method ofremoving extruder screw 80, may begin by detaching extruder screwcoupling 81 from the servomotor 38 and gearbox 39 assembly and detachingthe feed housing plate 48 from the transition housing 37. Then, theextruder drive assembly (e.g., the servomotor 38, gearbox 39, andtransition housing 37) may be slid along rails 44 and 45 to clear theextruder screw 80. Next, the extruder drive assembly may be rotated toallow the removal of the extruder screw 80 and screw coupling 81. Forexample, the extruder drive assembly may be rotated by removing a boltfixing transition housing 37 to support plate 85 and rotating hinge leaf87 with the extruder drive assembly, providing a removal path forextruder screw 80 and screw coupling 81 that does not interfere with theextruder drive assembly.

With continued reference to FIG. 5, a method of servicing CNC machine 1and/or replacing components thereof may include removal and replacementof a melt core of the print head 99. The melt core includes feed housing40, extruder 61, and melt pump 62. The components of the melt core maydetermine the throughput of the print head. A method of removing andreplacing the melt core may include detaching servomotor 38, gearbox 39,and transition housing 37 from extruder screw 80 and feed housing 46.Next, heaters 41, and one or more thermocouples, may be disconnectedfrom the controller. Then, the extruder drive assembly (servomotor 38,gearbox 39, and transition housing 37) may be moved along rails 44 and45 and secured in a new location. For example, the extruder driveassembly may be slid upwards along rails 44 and 45 with support plate85. Next, melt pump 62 may be disconnected from the carrier 25. The meltcore or a component thereof may be removed. A different melt core (orcomponent thereof) may be positioned in the print head 99, and attachedto the melt pump 62 and/or the carrier 25. Next, heaters 41, and one ormore thermocouples may be reconnected to the controller. Then, theservomotor 38, gearbox 39, and transition housing 37 may be moved alongrails 44 and 45, for example by sliding support plate 85, and attachedto the feed housing plate 48 and extruder screw 80.

With reference to FIGS. 6A and 6B, a second liquid cooling system mayextend from an inlet 100 connected to servomotor 38. The second liquidcooling system may include a gearbox cooling coil 101 disposed aroundgearbox 39 and continue along a path to, feed housing 40, a feed throat102, and a melt pump gearbox mount plate 104. The second liquid coolingsystem may also include an exit 103 which provides a return path to achiller or other heat exchanger. The second liquid cooling system mayprovide liquid coolant to one or more components of the assembly, suchas the extruder servomotor (e.g., servomotor 38), feed housing 40, andone or more components within melt pump gearbox mounting plate 104. Acoolant, such as a liquid coolant, may include water, antifreeze,ethylene glycol, diethylene glycol, propylene glycol, betaine, or anyother suitable liquid coolants or combinations thereof.

Coolant may enter through inlet 100 to cool servomotor 38 and travelwithin gearbox cooling coil 101 to cool gearbox 39. Coolant may thenenter a path internal to feed housing 40, as shown in FIG. 6B. Next,coolant may exit feed housing 40 and pass into a path within or alongfeed throat 102 before entering melt gearbox mounting plate 104. Afterexiting an interior of melt gearbox mounting plate 104, coolant mayreturn to the chiller or other heat exchanger via exit 103. Additionalcomponents may be cooled by the second liquid cooling system.Additionally, the second liquid cooling system may include a pluralityof separate and/or independent coolant systems.

From the foregoing detailed description, it will be evident that thereare a number of changes, adaptations and modifications of the presentdisclosure which come within the province of those persons havingordinary skill in the art to which the aforementioned disclosurepertains. However, it is intended that all such variations not departingfrom the spirit of the disclosure be considered as within the scopethereof as limited by the appended claims.

1-20. (canceled)
 21. A method of assembling an additive manufacturingsystem, the method comprising: securing one or more rails to a carrierof an additive manufacturing apparatus; providing an extruder on thecarrier of the additive manufacturing apparatus; attaching an extruderdrive assembly to the carrier such that the extruder drive assembly ismoveable relative to the extruder along the one or more rails; providingan opening in the extruder sized for removal of at least a part of theextruder; and securing the extruder drive assembly to the extruder suchthat the extruder drive assembly is detachable from, and reattachableto, the extruder.
 22. The method of claim 21, wherein the extruder driveassembly includes a transition housing that is detachable from a feedhousing of the extruder.
 23. The method of claim 21, wherein theextruder drive assembly, when detached from the extruder, is pivotalrelative to the extruder.
 24. The method of claim 21, wherein theopening in the extruder is sized for removal of an extruder screwextending within the extruder.
 25. The method of claim 21, furtherincluding securing a liquid cooling system to the additive manufacturingsystem, including a portion for cooling the extruder drive assembly anda portion for cooling a pump downstream of the extruder.
 26. The methodof claim 21, wherein securing the extruder drive assembly to theextruder includes slidably attaching the extruder drive assembly to theone or more rails.
 27. The method of claim 21, wherein the opening ispositioned adjacent to the extruder drive assembly when the extruderdrive assembly is attached to the extruder.
 28. The method of claim 27,wherein the additive manufacturing system includes a first extruderscrew and a second extruder screw that have at least one differentcharacteristic, the characteristic being length, pitch, helix angle,diameter, root, channel depth, channel width, channel flight, pushingflight, or trailing flight.
 29. The method of claim 28, wherein thefirst extruder screw, when inserted through the opening and operablyconnected to the extruder drive assembly, produces a different materialflow rate as compared to when the second extruder screw is insertedthrough the opening and is operably connected to the extruder driveassembly.
 30. A method of assembling an additive manufacturingapparatus, the method comprising: installing an assembly of an additivemanufacturing apparatus, and a carrier of the additive manufacturingapparatus, such that the assembly is moveable with respect to thecarrier; providing a removable component of the extruder such that theremovable component is positionable within the extruder; connecting theassembly to the removable component of the extruder; and connecting theassembly to the extruder such that the assembly abuts the extruder, theassembly being positionable away from the extruder when the assembly isdisconnected from the extruder and connected to the carrier.
 31. Themethod of claim 30, wherein the assembly includes a motor that isrotatably positionable in a direction away from the extruder.
 32. Themethod of claim 31, wherein the motor is rotatably positionable in thedirection away from the extruder with a hinge.
 33. The method of claim32, wherein the assembly of the additive manufacturing apparatusincludes a servomotor connected to the hinge, such that the servomotoris slidable with the hinge away from the extruder.
 34. The method ofclaim 30, further including securing a liquid cooling system to theadditive manufacturing apparatus, the liquid cooling system including aportion for cooling the removable component and a portion for cooling apump downstream of the extruder.
 35. A method of assembling an additivemanufacturing apparatus, comprising: providing an extruder and a carrierof the additive manufacturing apparatus; securing an assembly, includingan extruder-driving component, to the carrier of the additivemanufacturing apparatus such that the extruder-driving component of theadditive manufacturing apparatus is moveable toward the extruder by arotational motion and by a translational motion; providing an opening inthe extruder that faces the assembly when the assembly is secured to theextruder, a part of the additive manufacturing apparatus extendingthrough the opening; and securing the assembly, including theextruder-driving component, to the extruder.
 36. The method of claim 35,further including connecting the extruder-driving component to the part.37. The method of claim 35, wherein the extruder-driving component isslidable along a rail secured to the carrier when the extruder and theextruder-driving component are separated from each other.
 38. The methodof claim 35, further including attaching a cooling system to theadditive manufacturing apparatus, the cooling system including a portionfor cooling the extruder-driving component and a portion for cooling apump downstream of the extruder.
 39. The method of claim 38, wherein thecooling system is a liquid cooling system.
 40. The method of claim 39,wherein the portion for cooling the extruder-driving component cools agearbox and the portion for cooling the pump is downstream of theportion for cooling the gearbox.